6.5x55mm using Barnes ttsx 120gr - good development with Viht N540

[zambezi]

In a previous thread I attempted to replicate the 6.5x55mm loads that others had developed using N160. In common with at least two others on this forum, no amount of tinkering could get N160+Barnes_120gr+Blaser_6.5x55 to work.

So I have switched powders and it has been revelatory: all other parameters remain unaltered, but now some useful MVs and promising accuracy. Details of final rung in today's ladder:

CBTO = 2.337", jump = 252thou, 40gr N540, MV = 2800fps as measured with Magnetospeed V3, zero over-pressure signs on cases, clean extraction, post-shooting vernier checks show no growth in obturation pre-vs-post firing. I.e. these reloads were made with once-fired Sako brass. Today's testing was their second firing in the same rifle, and case dimensions have not altered. Case girth at widest point near head remains 0.479", shoulder height remains 1.765" for all 6 cases fired today regardless of powder charge used.

 

[mallettn]

That's interesting, thanks for posting. What length is your Blaser barrel?

 

[zambezi]

What length is your Blaser barrel?

520mm

 

[mallettn]

I have a similar length barrel on a 6.5 x 55 and am targeting 2800 to 2900 with 110 gn copper so your speeds are reassuring.

 

[JH83]

I have a similar length barrel on a 6.5 x 55 and am targeting 2800 to 2900 with 110 gn copper so your speeds are reassuring.

I would think you’d get a lot more than that.

I’m getting 3300fps with ease with 100gn TTSX and RS60 powder. Albeit a 26” barrel. We got to a nip under 3400 without pressure signs but backed off as the accuracy node was in the 3275fps range.

 

[mallettn]

That sounds achievable but pretty quick even given perhaps 180 odd fps for the barrel length difference. With the 110gn Quickload suggests about 3100 fps could be achieved with my barrel / bullet / powder choice but i would look to back off that by 150-200 fps.

 

[zambezi]

Mixed bag today. Still sifting notes and data and not 100% sure what to make of some of the results. Because I was getting some unexpected POI variation during today's session, I shot two mini batches of factory ammo between strings of reloads. The fact that they were no better made me wonder if something else is amiss with this caliber. [I was shooting sub moa with both .223 and 30.06 in same session, so doubt it was me]

I started with the lower loads and POI and ES variation were rather unexpected.



Next up were the two 40gr N540 shots at center target. They struck low and right. So I put two factory rounds into the lower left target. Also low and right. Finally, I removed the Magnetospeed V3 chrono bayonet and shot the rest of the 40gr N540 rounds into the top right target. The group does appear to have risen with the chrono removed from testing. Which is odd as it did not seem to have any impact last time out and affected neither my .223 nor 30.06 in the same session. But horizontal stringing is just bizarre.

I think I will sleep on this one and revisit after a few days. One hazy thought is this: I have been toying with a reduced neck tension using various bushing dies. There seems to be a mirror image shift between pairs of shots which would have been loaded together. Could the reduced neck tension have resulted in a bullet shift in the cartridge carried in the magazine? i.e. the second bullet in each loaded pairing had a different COAL to its chum?

 

[zambezi]

I have distilled my 6.5x55mm Viht N540+Barnes 120gr ttsx data into one MV graphic. Having all the MV data correlated on one page makes cross-referencing with target grouping data more profitable.

What I can see is that ES shrinks as N540 load approaches 40gr. Per GRT, 40gr is towards the upper end of possible N540 loadings [Viht have 41.5gr as max N540 load for 120gr projectile]. But I do not need more than 2800fps, so comfortable with a 40gr-ish N540 ceiling.

And somewhere around 39.8gr there is both low ES and good grouping. The next round of testing will focus on testing for good groups, leaving the Magnetospeed bayonet off the rifle. I do not have any absolute evidence that the chrono affects POI, but having narrowed the ES to sub 1%, I can now concentrate on groups by varying CBTO with no other variables in play. [all testing thus far has CBTO = 2.337"]

What is very encouraging is that there are multiple strings where the ES is in single digits [see chrono insert on graph]. As I get better at standardising brass prep [uniform case length, FL sizing, consistent neck tension, etc] I imagine that ES will improve with fewer outliers. Certainly there is a node hereabouts worth chasing down.

As ever, the disclaimer is that this is my load development. It is not a guide or recommendation to others.

 

[malmick]

Hi @zambezi just checking, in your first post you have a 1/4 inch jump?

 

[zambezi]

Per Erik Cortina's tutorial last month, there are three snugness states a chambered round can enjoy: "jump", "just-touching" and "jam".

He explains that chasing the lands is an unproductive excercise and unrelated to accuracy. But he says to avoid "jam" at all costs. To measure "jam" you make a longer-than-usual-COAL dummy round and use the closing bolt and lands to reduce the COAL. The extracted dummy case is now at the "jam" length.

By this method I have established that there is a1/4 inch [250thou] between my reloads which are at 2.337" CBTO, and the extracted dummy round which was at 2.589". [Actually, I made up 5 dummy rounds. This measurement is average thereof although none of the measurements deviated by more than 0.003"]

 

[Ronin]

Suggest you change powder choice - RS 60 works well in “55” - possibly suitable for 120’s but please check before using

As per Eric’s video chasing the lands is not something done any more by serious accuracy aficionados (like neck sizing )

 

[zambezi]

Suggest you change powder choice - RS 60 works well in “55” - possibly suitable for 120’s but please check before using

I have come too far down this N540 development road to quit at the final hurdle. Below is the target that aligns to the chrono series #55 shots highlighted in the earlier graphic. We are talking touching POI! Albeit with some very odd vertical stringing.

What I suspect is that I changed my shooting position intra day which is hardly an optimum test situation. My Pro Success stock is one of the earlier ones: it has some flex in the forend. Later models are stiff and cannot be warped by hand.

If you support my rifle [either on the bench or on quad sticks] close to the barrel end of the forend, you can deflect the forend upwards and close the free-floating-barrel gap. It takes some dicipline and awareness to keep the forward support position 12cm+ back towards the trigger set.

I suspect the vertical stringing below goes away with better management of the forend/free-float-gap. At that point I am expecting a ragged hole.

 

[25 Sharps]

I have come too far down this N540 development road to quit at the final hurdle. Below is the target that aligns to the chrono series #55 shots highlighted in the earlier graphic. We are talking touching POI! Albeit with some very odd vertical stringing.

What I suspect is that I changed my shooting position intra day which is hardly an optimum test situation. My Pro Success stock is one of the earlier ones: it has some flex in the forend. Later models are stiff and cannot be warped by hand.

If you support my rifle [either on the bench or on quad sticks] close to the barrel end of the forend, you can deflect the forend upwards and close the free-floating-barrel gap. It takes some dicipline and awareness to keep the forward support position 12cm+ back towards the trigger set.

I suspect the vertical stringing below goes away with better management of the forend/free-float-gap. At that point I am expecting a ragged hole.

View attachment 173475

They will all kill deer at reasonable distances, why try harder?

You are surpassing Barnes' own velocities, https://www.barnesbullets.com/wp-content/uploads/2017/08/6.5x55-Swed.pdf

In terms of gap you need to shoot groups in whatever likely position you will be shooting deer from to see if they are acceptable if not you need to look at your stock otherwise you'll be subconsciously measuring 120 mm when on aim and the deer will disappear over the horizon.

 

[25 Sharps]

I would think you’d get a lot more than that.

I’m getting 3300fps with ease with 100gn TTSX and RS60 powder. Albeit a 26” barrel. We got to a nip under 3400 without pressure signs but backed off as the accuracy node was in the 3275fps range.

What charge and COAL out of interest?

N540 lags behind RS60 velocity wise according to QL whether that is for the 100s or 120s

 

[Ronin]

No problem, was just a suggestion as I thought the groups appeared to be “loose”

The vertical stringing on the last target could be forend pressure or head position aligning the scope

All are killing shots

Providing you are not shooting far would that not suffice ,?

 

[25 Sharps]

What I can see is that ES shrinks as N540 load approaches 40gr. Per GRT, 40gr is towards the upper end of possible N540 loadings [Viht have 41.5gr as max N540 load for 120gr projectile]. But I do not need more than 2800fps, so comfortable with a 40gr-ish N540 ceiling.

Depends which projectile you look at and which data for that matter

You are referring to the 6.5x55 swedish mauser 120 gr sierra HPBT, the 120 gr Barnes bullet doesn't list the powder at all.

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If you go to the Skan data 43.4 is listed as max - this is for a scenar bullet is likely a shorter than the barnes bullet so COAL will need adjusting to manage pressure

Rifle reloading data | Handloading | Rifle calibers | Centerfire Rifle bullets | Reload your own ammo - Vihtavuori

Vihtavuori offers rifle reloading data for numerous calibers and bullets for match and hunting purposes. Never exceed maximum loads.

www.vihtavuori.com

 

[zambezi]

They will all kill deer at reasonable distances, why try harder?

Some of the hunting I do with this rifle is in Africa. I have taken Waterbuck, Wildebeest, Impala and Red Hartebeest with it in South Africa and Namibia.

In some cases the first shot is over 200m. That requires maximum accuracy and good MV to deliver an ethical shot. Perfecting one round that can be used for both domestic and foreign use is part of the design brief.

In terms of gap you need to shoot groups in whatever likely position you will be shooting deer from to see if they are acceptable if not you need to look at your stock otherwise you'll be subconsciously measuring 120 mm when on aim and the deer will disappear over the horizon.

I have neck damage and never shoot prone. I almost always use quad sticks. If I cannot, I am happy to let shot pass. In five years of using this rifle I have always managed to make that final check before pulling the trigger on live quarry. As an aid to doing that, I have also I have set the top-strap on my quad sticks such that the gape between forward and rear "Vs" are limited. Thus when I offer up the pistol grip to the rearward "V", the forward "V" is distal from the forend tip.

But I agree it is sub-optimum. I have been shopping for a later stock, but none have presented at the right price. One other option might be to increase the barrel-to-stock gap, or attempt to stiffen the stock with epoxy in its voids.

 

[zambezi]

The vertical stringing on the last target could be forend pressure or head position aligning the scope

I use a second focal plane Z6i and set parallax at the top of the day. I do not make any scope adjustments during any testing session. So provided the reticle-to-target image appears the same to my eye, the point of aim should remain unchanged, right? Or am I missing something here?

 

[25 Sharps]

I use a second focal plane Z6i and set parallax at the top of the day. I do not make any scope adjustments during any testing session. So provided the reticle-to-target image appears the same to my eye, the point of aim should remain unchanged, right? Or am I missing something here?

No, if your head is aligning differently with the scope for the shots parallax will change the POI

 

[JH83]

What charge and COAL out of interest?

N540 lags behind RS60 velocity wise according to QL whether that is for the 100s or 120s

49.6g and 2.940

3380fps with 100gn TTSX albeit through a 26” barrel.